The low melting glass is often used for sealing the gap of such glass panel as above because it has superior adhesive property to e.g. metal solder. Conventionally, the low melting glass in the form of paste would be applied to the peripheral edges of the two glass sheets and heated to 480° C. or higher, thereby to render the low melting glass into melted state. Then, it would be cooled to the normal temperature for solidification, whereby the peripheral edges of the glass sheets were bonded for sealing the gap.
However, since the low melting glass has good adhesive property for the glass sheets, the glass under its melted state also has good wettability to the glass sheets. Then, as shown in FIG. 8, in a cross section substantially normal to the faces of the glass sheets 1, 2, an adjacent face 4b of the low melting glass 4 adjacent the gap V is formed as a concave face with its center portion between the glass sheets 1, 2 extending away from the gap V.
Then, according to the convention, the glass would be cooled and hardened directly under such condition. Hence, in the conventional glass panel, the adjacent face 4b of the low melting glass 4 adjacent the gap V is formed as a concave face with its center portion between the glass sheets 1, 2 extending away from the gap V.
Therefore, with the conventional glass panel, at opposed ends of the adjacent face 4b of the low melting glass 4, there are formed sharp edged portions 4c contacting the glass sheets 1, 2 and projecting toward the gap V. then, for instance, when a wind pressure acts on the faces of the glass sheets, as denoted by arrows in FIG. 8, thereby to apply a force which tends to displace the two glass sheets 1, 2 closer to each other, there occurs stress concentration at the sharp edged portions 4c at the opposed ends of the adjacent face 4b and the two glass sheets 1,2 will tend to be bent in the mutually approaching direction, thus tending to bend the sharp edged portions 4c. As a result, the sharp edged portions 4c would often be cracked and damaged.
Moreover, when the sharp edged portions 4c are damaged, due to the characteristics of the low melting glass vulnerable to brittle fracture, the crack would develop from that damaged portion. For this reason, the conventional glass panel has a shortcoming in the strength of the low melting glass used for bonding and sealing the peripheral edges of the two glass sheets. This shortcoming would appear especially conspicuously with a vacuum double glazing with the gap between the opposed glass sheets being maintained under a depressurized state.
The present invention addresses to such shortcoming of the convention and its object is to provide a glass panel which even when constructed as a vacuum double glazing, can effectively prevent damage in the low melting glass portion thereof by improving the strength of the low melting glass used at the peripheral edges of the two glass sheets.